COMPOSITION FOR SIZING PAPER

Abstract

A composition for sizing paper includes alkenylsuccinic anhydride (ASA) as the sizing agent and an emulsifier system of anionic emulsifiers and nonionic components, wherein the anionic emulsifiers are chosen from alkali metal salts of aliphatic carboxylic acids or aliphatic dicarboxylic acids and the nonionic components are chosen from polyethylene glycols.

Claims

1. A process for the preparation of a composition for sizing paper, the process comprising: generating an anionic emulsifier in situ by adding sodium hydroxide or potassium hydroxide to a sizing agent comprising alkenylsuccinic anhydride (ASA) having an alkenyl chain length of from 12 to 24 C atoms, to form sodium or potassium salts of an alkenylsuccinic acid having an alkenyl chain length of from 12 to 24 C atoms; and adding nonionic components comprising polyethylene glycols having an average molecular weight of from 200 to 8000, to form the composition.

2. The process of claim 1, wherein the composition is emulsified with an aqueous phase under low shearing forces.

3. The process of claim 2, wherein the aqueous phase further comprises starch.

4. The process of claim 1, wherein generating the anionic emulsifier in situ comprises heating the sodium hydroxide or potassium hydroxide and the sizing agent at a temperature of from 100 to 140° C.

5. The process of claim 1, wherein the alkenylsuccinic acid has an alkenyl chain length of from 16 to 18 C atoms.

6. The process of claim 1, wherein the anionic emulsifier and the non-ionic components are present in an amount of up to 5 wt. %, based on the alkenylsuccinic anhydride.

7. The process of claim 1, wherein the anionic emulsifiers to non-ionic components are at a weight ratio from 1:10 to 10:1.

Description

EXAMPLE 1

[0019] This example shows the sizing efficiency as a function of the emulsifiers or emulsifier systems employed.

[0020] Since the relevant parameter in sizing of paper is the sizing efficiency or the hydrophobizing action, the sizing was in each case checked with the aid of laboratory sheets after a change in the emulsifier/emulsifier system. For this, the Cobb 60 value (called Cobb 60 in the following), which describes the water uptake in g/m.sup.2 in 60 seconds, was used.

[0021] To test the ASA emulsifier mixtures, a laboratory sheet-forming unit, the Rapid-Kothen system, was used. The pulp used was a bleached sulphate pulp with a 70% long fibre and 30% short fibre content, ground to a Schopper-Riegler freeness of 30°.

[0022] Emulsifying process with high shearing forces:

[0023] In order to be able to evaluate the efficiency of an emulsifier system, an emulsifier-free ASA (AS 1000) as a standard was emulsified as the sizing agent in the conventional manner, i.e. using very high shearing forces. 1 part of liquid sizing agent was added to 99 parts of a 4% strength cationic starch solution (Hicat 5103 A) and the mixture was then emulsified for one minute with a shearing apparatus (Ultraturrax) at 10,000 revolutions per minute. This emulsion was diluted 1:10 with water and an aliquot of this dilution was employed for sizing a laboratory sheet.

[0024] A modified emulsifying process with which it is not possible to prepare an emulsion which achieves a satisfactory sizing efficiency if an emulsifier-free sizing agent is used was now contrasted with this emulsifying process.

[0025] Emulsifying process with low shearing forces:

[0026] This emulsifying process comprises emulsification of 5 parts of the sizing agent with 95 parts of water for one minutes with a shearing apparatus (Ultraturrax) at only 4,000 revolutions per minute. 20 g of the pre-emulsion obtained in this way are now stirred into 80 g of 5% strength cationic starch solution. This emulsion is now diluted 1:10 with water and an aliquot of this dilution is employed for sizing a laboratory sheet.

[0027] Various anionic or nonionic emulsifiers/components and mixtures thereof were now added to the ASA, laboratory sheets were formed and sizing tests were carried out. The results can be seen from the following tables:

TABLE-US-00001 TABLE 1a Sizing values after addition of anionic emulsifiers. The sizing values are stated in Cobb 60 [g of water uptake/m.sup.2]. Cobb 60 [g/m.sup.2] Amount High Low of size shearing shearing [kg/t of forces forces paper] No emulsifier 22 85 1.0 (comparison)   1% Dioctyl — 90 1.0 sulphosuccinate 0.1% Na-ASA — 95 1.0   1% Na-ASA — 92 1.0 0.3% Na-ASA — 88 1.0   1% K-ASA — 95 1.0 0.3% heptadecanoic — 92 1.0 acid K salt

[0028] In the above Table as well as in the following description Na-ASA means alkylsuccinic acid sodium salt and K-ASA means alkylsuccinic acid potassium salt.

[0029] The table shows that when using the anionic emulsifiers employed, no improvement in sizing occurs when low shearing forces are applied.

TABLE-US-00002 TABLE 1b Sizing values after addition of nonionic component. The sizing values are stated in Cobb 60 [g of water uptake/m.sup.2]. Cobb 60 [g/m.sup.2] Amount of size High shearing Low shearing [kg/t of paper] forces forces No emulsifier 22 85 1.0 0.5% PEG 2000 — 72 1.0   1% PEG 2000 — 52 1.0 1.5% PEG 2000 — 55 1.0

[0030] The table shows that when using the nonionic component PEG 2000 an improvement in sizing occurs when low shearing forces are applied.

TABLE-US-00003 TABLE 1c Sizing values after addition of various nonionic emulsifiers/ components in combination with 0.3 wt. % of Na-ASA (alkylsuccinic acid sodium salt) as an anionic emulsifier. The sizing values are stated in Cobb 60 [g of water uptake/m.sup.2]. Cobb 60 [g/m.sup.2] Amount of size Low shearing forces [kg/t of paper] 0.5% PEG 2000 30 1   1% PEG 2000 25 1 0.5% Empilan KCL 5 77 1 0.5% Empilan KCL 5 71 1 0.5% Walloxen ID 30 83 1 0.5% Walloxen LM 100 52 1 0.5% Walloxen SH 20 PF 94 1 0.5% Walloxen SH 30 70 PF 66 1 0.5% Walloxen SH 55 95 PF 82 1

[0031] Empilan and Walloxen are trademarks for nonionic emulsifiers based on fatty alcohol ethoxylate or fatty acid ethoxylate.

[0032] The table shows that by the combination according to the invention of the specific anionic emulsifiers with polyethylene glycol as a nonionic component an improvement in the sizing efficiency is achieved. This improvement furthermore exceeds that which was to be expected for this specific combination on the basis of the results when the particular emulsifiers/components are used by themselves (Table 1a and 1b). It can furthermore be seen from Table 1c that this synergistic effect does not occur in combinations of the specific anionic emulsifiers with other nonionic emulsifiers, such as are illustrated by Empilan and Walloxen.

EXAMPLE 2

[0033] In this example the sizing efficiency of various combinations of anionic emulsifiers and nonionic components was investigated. In this context, the materials and preparation processes employed in Example 2 and the test methods described therein were used. The emulsification in each case took place using low shearing forces.

TABLE-US-00004 TABLE 2 Sizing values after addition of various polyethylene glycols in combination with anionic Na-ASA. The sizing values are stated in Cobb 60 [g of water uptake/m.sup.2]. PEG PEG PEG Na-ASA Cobb 60 200 [%] 2000 [%] 4000 [%] [%] [g/m.sup.2] 0.5 — — 0 84 1 — — 0 92 1 — — 0.3 79 — 1 — 0.3 25 — 1 — 1 25 — — 0.5 0.3 36 — — 0.5 0.7 53 — — 1 0.3 57 — — 1 1 44

[0034] The experiments show that combinations of Na-ASA and polyethylene glycols show an improved sizing efficiency compared with the use of polyethylene glycols by themselves. The most significant improvement was achieved in this context with a combination of Na-ASA (0.3%) with PEG 2000 (1%)

EXAMPLE 3

[0035] An ASA composition according to the invention (comprising ASA and a combination of Na-ASA (0.3%) with PEG 2000 (1%)) or AS 1000 (a conventional emulsifier-free ASA) and a 4% strength starch solution (Hicat 5103 A) were sucked in over a laboratory water-jet pump and emulsified via the water jet. The particular flow ratios of ASA, starch and water were chosen such that a 1% strength ASA emulsion was obtained. Finally, this was employed for sizing laboratory sheets.

TABLE-US-00005 TABLE 3 Amount of size [kg/t of paper] Cobb 60 [g/m.sup.2] AS 1000 0.35 76 0.5 52 0.75 32 1 23 ASA composition 0.25 74 according to the invention 0.5 33 0.75 27 1 26

[0036] The table shows that with the exception of the amount of size of 1 kg/t (oversizing), lower Cobb 60 values and therefore an improved sizing efficiency can be achieved consistently by using the ASA composition according to the invention.

EXAMPLE 4

[0037] Using three paper sizing compositions, sizing emulsions were prepared and the particle size thereof was determined immediately after the preparation and also 30 and 60 min thereafter. The Cobb 60 value of laboratory sheets which was achieved with a fresh emulsion and also with an emulsion aged for 60 min was furthermore determined.

[0038] The sizing agents employed are an ASA composition according to the invention (comprising ASA and a combination of Na-ASA (0.3%) with PEG 2000 (1%)) and AS 1000 (ASA without addition of emulsifier). The density of all the compositions before emulsification thereof with a starch-containing phase was 0.95 g/ml. Liquid starch of the Vector brand from Roquette with a concentration of 3.00 wt. % was employed as the starch. The emulsification was carried out via an aperture of 1.9 mm diameter under a pressure of 20 bar with a starch flow of 440.00 l/h and an ASA flow of 14.00 l/h. Amounts which in each case corresponded to 0.74 kg of ASA/t of paper were employed in the sizing experiments.

[0039] The particle size was measured by means of static light scattering with a Horiba LA-300 measuring apparatus. The volume distribution in water at a relative refractive index of 1.10 was determined. The value stated for the particle size in μm corresponds to that which was determined for 90% of the particles.

[0040] The results for the particle sizes and the Cobb 60 values are shown in the following table.

TABLE-US-00006 TABLE 4 ASA composition according to the invention AS 1000 Particle size (90%) 2.10 4.40 after 0 min [μm] Cobb 60 after 0 min [g/m.sup.2] 30 35 Particle size (90%) 2.1 (30 min) 4.50 after 60 min [μm] Cobb 60 after 60 min [g/m.sup.2] 31 38

[0041] The table shows that when liquid starch (Vector; Roquette) was used, it was possible to achieve both the smallest particles and the best sizing efficiency with the ASA composition according to the invention by emulsification at room temperature. This was also still the case after the emulsion had been stored for one hour.

EXAMPLE 5

[0042] Various sizing emulsions were prepared using an ASA composition according to the invention (comprising ASA and a combination of Na-ASA (0.3%) with PEG 2000 (1%)) and AS 1000 (an emulsifier-free ASA) and the particle size thereof was determined immediately after the preparation and also 20 min thereafter. The Cobb 60 value of laboratory sheets which was achieved with a fresh emulsion and also with an emulsion aged for 20 min was furthermore determined.

[0043] The ASA concentration of the compositions before emulsification thereof was 1.86%. An 80% strength potato starch (Cationamyl 9852) was employed as the starch in the aqueous phase in a concentration of 2.00%, based on ASA. The emulsification was carried out via an aperture of 1.9 mm diameter under a pressure of 20 bar and at a temperature of from 75 to 82° C. with a starch flow of 445.00 l/h and an ASA flow of 8.70 l/h. Amounts which in each case corresponded to 0.81 kg of ASA/t of paper were employed in the sizing experiments.

[0044] The results for the particle sizes and the Cobb 60 values are shown in the following table.

TABLE-US-00007 TABLE 5 ASA composition according to the invention AS 1000 Particle size (90%) 2.90 5.80 after 0 min [μm] Cobb 60 after 0 min [g/m.sup.2] 34 35 Particle size (90%) 3.40 4.50 after 60 min [μm] Cobb 60 after 60 min [g/m.sup.2] 38 38

[0045] The table shows that when an 80% strength potato starch is used and with emulsification at elevated temperatures, good sizing values and particle sizes are achieved with the ASA composition according to the invention compared with the conventional sizing composition based on AS 1000. In contrast, the particle size of 5.8 μm shows that it was not possible to emulsify AS 1000 by this method.

EXAMPLE 6

[0046] Using three paper sizing compositions based on an ASA composition according to the invention (comprising ASA and a combination of Na-ASA (0.3%) with PEG 2000 (1%)), AS 2000 (an ASA with an anionic emulsifier) and AS 1000 (an emulsifier-free ASA), size emulsions were prepared by first emulsifying with pure water via an aperture of 1.9 mm diameter under a pressure of 20 bar, without using starch, a water flow of 440.00 l/h and an ASA flow of 9.00 l/h being used. The ASA concentration of the compositions before emulsification thereof was 1.94%. The emulsions obtained in this way were then stirred into a starch solution (Cationamyl 9852) at 37° C., so that a 0.1% strength size emulsion was obtained. These size emulsions were then employed for the sizing tests in amounts which in each case corresponded to 0.84 kg of ASA/t of paper.

TABLE-US-00008 TABLE 6 ASA composition according to the invention AS 2000 AS 1000 Particle size (90%) 4.80 4.00 7.80 in water [μm] Particle size (90%) 4.90 5.70 9.10 in starch [μm] Cobb 60 [g/m.sup.2] 27 76 67 Comments 2 phases 2 phases

[0047] As the table shows, an emulsion which was still stable was achieved for the sizing emulsion which contained the ASA sizing composition according to the invention, in spite of the large particle size, while phase separation already occurred when the sizing agents AS 2000 and AS 1000 were used. A satisfactory sizing action was furthermore achieved with the sizing emulsion containing the sizing composition according to the invention.